The present invention relates to a bipolar forceps for endoscopes, and more particularly, to a bipolar forceps having two end effectors between which high frequency voltage is to be applied.
Endoscopic operation such as cutting and/or coagulating internal tissues are frequently performed using a mono-polar forceps. When the mono-polar forceps is employed, one internal electrode is inserted into a patient through an endoscope, while another ground electrode is placed on the skin of the patient. A high frequency voltage is applied to the internal electrode so that the tissue at the internal electrode is cut and/or coagulated by electric current flowing between the internal electrode and the ground electrode.
The electric current, however, does not flow only between the internal electrode and the ground electrode but also to any other conductors that are in contact with the patient, if there is any, and this kind of current flow decreases the amount of electric current that affects the operation of the tissue. Further, electric current may also flow through a surgeon who unintentionally touches the patient during the operation.
Japanese Patent application provisional publication P2000-271128 discloses a bipolar forceps for endoscopes that overcomes the above mentioned problems of the mono-polar forceps. The disclosed bipolar forceps includes a pair of electrodes provided at the distal end of a flexible sheath, which is remotely operated from the proximal end of the flexible sheath to open and close in a scissors-like action. High frequency voltage is applied between the two electrodes to cut and/or coagulate the internal tissue located between the electrodes.
It is important for the bipolar forceps to ensure electric insulation between the two electrodes, which is difficult since the electrodes are located in the immediate vicinity of each other. In order to achieve the electric insulation between the electrodes, the forceps disclosed in the above mentioned Japanese application employs electrodes made of nonconductive materials such as plastics and ceramics, partially applied with metal coatings on the surface thereof by means of vaporization.
Electrodes made of plastics or ceramics, however, are easy to be damaged during repetitive use due to their insufficient strength. In addition, the metal coatings on the electrodes tends to wear out due to friction between the electrodes and endoscope during the advance and retraction of the forceps through the endoscope.
The present invention provides the advantage in that, in a bipolar forceps for endoscopes, electric insulation between the electrodes is structurally achieved and thus electrodes made of materials having practically sufficient strength for repetitive use can by employed.
According to embodiments of the invention, there is provided a clevis, two shafts, and two end effectors. The clevis has two arms that form a slot between them. The shafts are sustained between the two arms spaced apart from each other. Each of the end effectors is pivotably attached to a different one of the two shafts, respectively, such that the end effectors are able to move in a scissor-like action. The end effectors are made of conductive material. Thus the end effectors can be utilized as electrodes for applying a high frequency voltage between them.
Since the two end effectors are separately sustained by different shafts, respectively, short circuit does not occur between the end effectors during the application of high frequency voltage to them although the end effectors are made of conductive material.
The two shafts may be arranged in parallel to each other. Further, each of the shafts may be arranged to cross the slot perpendicularly.
Optionally, the two shafts may be located on opposite sides with respect to the center axis of said clevis, respectively. In this case, the two shafts may further be located at a same distance from the center axis of the clevis.
The shafts and/or the end effectors may be made of metal in order to increase the durability of the forceps. The clevis may be made of non-conductive material so that no short circuit between the end effectors will be established via the clevis.
Optionally, the bipolar forceps of the invention may include two cylindrical insulators each provided on a different one of the two shafts, respectively, in order to insulate the end effectors from the shafts. Such insulators prevent the short circuit between the two end effectors even when fluid adheres to and bridges the two shafts.
In the above case, the cylindrical insulator may cover the shaft over the entire width of the slot that is formed between the arms of the clevis in order to prevent the short circuit effectively.
Optionally, the cylindrical insulator may include a small outer diameter portion for fitting the end effector thereon. This small outer diameter portion may have an outer diameter smaller than the outer diameter of an adjacent portion of the cylindrical insulator for keeping the end effector in place.
In the above case, one of said two cylindrical insulators may have the small outer diameter portion at the end thereof located besides one of the two arms, and the other of said two cylindrical insulators may have the small outer diameter portions at the end thereof located besides the other of the two arms, so that the end effectors held by the shafts are located spaced apart also in the slot width direction.
Optionally, each of the end effectors may be bent between a distal end of the end effector and a portion being attached to the shaft such that at least the distal ends of the end effectors meet each other when the end effectors are closed.